Image display apparatus

ABSTRACT

An image display apparatus of a projection-type is provided which includes an illuminator with a light source, an optical modulator illuminated by light illuminator and which makes spatial modulation of the illumination light according to a to-be-displayed image for either transmission or reflection, and a projection lens to form an image of the optical modulator. The apparatus includes also a first reflecting element to reflect, towards the light source, the unwanted light of the light beam emitted from the illuminator and which will not illuminate the optical modulator, and a second reflecting element to guide, by reflecting, the unwanted light once reflected by the first reflecting element. In the apparatus, the combination of the light source and illuminator, which can recycle the unwanted light efficiently in the projector, makes it possible to inexpensively separate and recombine polarized components of the light beam. Use of a single-plate optical modulator formed from a color filter permits to utilize the light with an improved efficiency. Also by adopting a single-plate optical modulator of a sequential color-type, it is possible to attain an improved efficiency of light utilization. Thus, the efficiency of light utilization of an optical modulator whose numerical aperture is small can be improved and the peak brightness on a dark screen can be elevated.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an image displayapparatus, and more particularly, to a projection-type image displayapparatus including an optical modulator which is illuminated by lightfrom an illuminator, and a projection lens which forms the modulatedlight from the optical modulator into an image.

[0003] 2. Description of the Related Art

[0004] A typical one of the conventional projection-type image displayapparatuses includes an illuminator, optical modulator (will be referredto simply as “modulator” hereunder) illuminated by light from theilluminator, and a projection lens which forms the modulated light fromthe modulator into an image. The conventional image display apparatususes a discharge lamp as the light source of the illuminator, and aliquid crystal as the modulator, and has a relatively large size.

[0005] Since the image display apparatus of the above type adopts acolor filter for each pixel of one modulator and a so-called sequentialcolor display method by which an image is displayed in colors on thetime-shared basis, so it is inexpensive. However, the apparatus is notadvantageous in that it cannot utilized light efficiently and consumesmuch power.

[0006] The reason why the apparatus cannot utilize the light with a highefficiency is that since the modulator is a non-luminous element whichmodulates the polarized state of incident light, a means is needed whichsplits a light beam emitted from a light source into rays of lightaccording to the polarized state of each ray and then recombines thesplit rays of light together, the light source emits light even when animage is displayed in black, which is different from a luminous-typeimage display apparatus, and the apparatus loses light correspondinglyto an light-utilization efficiency which depends upon the numericalaperture of the modulator.

[0007] For a higher efficiency of light utilization in the conventionalimage display apparatus, the following are done by the optical elementsetc. included in the image display apparatus.

[0008] [Splitting and recombination of polarized light components]

[0009] Referring now to FIG. 1, a conventional image display apparatusis schematically illustrated in the form of an axial-sectional view. Theabove-mentioned means for splitting a light beam emitted from a lightsource in an illuminator into rays of light according to the polarizedstate of each ray and then recombining the split rays of light togetheris known as a polarized-state converter. As shown, the illuminator usedin the image display apparatus includes a light source 101, modulator102, and a P-S converter 103 provided, as the polarized-state converter,between the light source 101 and modulator 102. The P-S converter 103 isformed as shown in FIG. 2. Namely, a glass block 108 is prepared byattaching glass plates 105 each having formed thereon a polarizedcomponent splitting layer 104 formed from a multilayer film of aninorganic substance and glass plates 107 each having a reflectingsurface 106 formed thereon alternately to each other. The glass block108 thus formed is sliced along cutting planes 109 laid obliquely inrelation to the joined surfaces of the glass plates 105 and 107 to makeP-S converter plates.

[0010] A light beam being a mixture of P- and S-polarized components,projected onto the P-S converter 103, is separated by the polarizedcomponent splitting layer into P- and S-polarized components. So, the P-and S-polarized components split by each of the layers of the P-Sconverter 103 will go out of the P-S converter 103. With a half-wave(λ/2) plate 110 provided at a portion of the P-S converter 103 at whichthe light will go out and corresponding to either the S- or P-polarizedray of light, the P-S converter 103 provides a light beam includingsolely either the P- or S-polarized component.

[0011] Use of the P-S converter 103 and half-wave plate 110 as apolarized component splitter permits to improve the efficiency of lightutilization of the illuminator used to illuminate the modulator whichmodulates polarized components of an incident light.

[0012] In the above illuminator, a light beam emitted from the lightsource 101 is reflected by a parabolic mirror 111 and incident upon theP-S converter 103 through a pair of fly-eye lenses 112 and 113. Then, itpasses through the half-wave (λ/2) 110 and a condenser lens 114 andreaches the modulator 102.

[0013] [Reflecting polarizer]

[0014] The conventional polarizer allows only one of two types ofpolarized components of an incident light to pass through whileabsorbing the other type of polarized component. However, there has beenproposed a “reflecting polarizer” which allows one of two types ofpolarized components of an incident light to pass through whilereflecting, not absorbing, the other type of polarized component. Use ofsuch a “reflecting polarizer” as the polarized-state converter permitsto utilize the other type of polarized component of the incident lightby reflecting it again, that is, to improve the efficiency of lightutilization.

[0015] [Linear polarizer using a birefringent multilayer film]

[0016] Also, there has been proposed a linear polarizer using abirefringent multilayer film formed by laminating two types of polymerfilms each being anisotropic in refractive index and different inrefractive index from each other and elongating the laminated films. Inthe linear polarizer, the laminated two types of polymer films arecompletely coincident in refractive index with each other in thedirection of one of axes of polarization while being not coincident inthe direction of the other polarization axis. By adjusting the differentrefractive indexes, it is possible to pass the polarized light in thedirection of one of the polarization axes while reflecting the polarizedlight in the direction of the other polarization axis perpendicular tothe one polarization axis. Thus, the “reflecting polarizer” can beprovided.

[0017] Note that the above “reflecting polarizer” is commerciallyavailable from the 3M under the trade name “DBEF” or “HMF”.

[0018] [Circular polarizer using a cholestetric liquid crystal]

[0019] As well known, the cholesteric liquid crystal selectivelyreflects light beams. There has been proposed a circular polarizerutilizing the property of the cholesteric liquid crystal to selectivelyreflect light beams. As disclosed in the Japanese Published UnexaminedApplication No. 281814 of 1994, since the cholesteric liquid crystal hasa pitch varying by more than 100 nm, it can selectively reflect lightbeams having wavelengths over the visible range. Also, awavelength-independent circular polarizer can be produced using such acholesteric liquid crystal polymer-made circular polarizer.

[0020] The circular polarizer formed from the cholesteric liquid crystalpolymer and polarized-state converter using the circular polarizer areknown from he disclosure in the Japanese Patent Gazette No. 2,509,372.The invention disclosed in this Gazette utilizes the fact that becauseof the characteristic of the circularly polarized light, namely, sincethe phase changes 180 deg. per reflection, a right-hand circularlypolarized light is converted to a left-hand one while a left-handcircularly polarized light is converted to a right-hand one. As shown inFIG. 3, the reflector or parabolic mirror 111 can be combined with acholesteric liquid crystal polymer layer 115 to build a polarizedcomponent splitting/recombination unit. The polarized componentsplitting/recombination unit using the above linear polarization needs ahalf-wave (λ/2) plate, but the polarized componentsplitting/recombination unit using the circular polarization needs nosuch half-wave plate.

[0021] More specifically, a light beam emitted from the light source 101is incident upon the cholesteric liquid crystal polymer layer 115through a condenser lens 116, while being reflected by the reflector orparabolic mirror 111 and incident upon the cholesteric liquid crystalpolymer layer 115 through the condenser lens 116. At the cholestericliquid crystal polymer layer 115, the circularly polarized light in onedirection will be allowed to pass through while the circularly polarizedlight in the other direction will be reflected. The circularly polarizedlight in the other direction, thus reflected by the cholesteric liquidcrystal polymer layer 115, is reflected by the reflector or parabolicmirror 111 to a circularly polarized light in the one direction,incident again upon the cholesteric liquid crystal polymer layer 115 andpassed through the latter.

[0022] However, the conventional image display apparatus including theaforementioned illuminator is not advantageous in the followingrespects:

[0023] [Manufacturing process]

[0024] The aforementioned illuminator can only be manufactured in acomplicated process and with high costs.

[0025] [Problems of the circular polarizer using the cholesteric liquidcrystal polymer]

[0026] The circular polarizer disclosed in the aforementioned JapanesePublished Unexamined Application No. 281814 of 1994 are independent ofany light wavelength, but cannot be said to satisfactorily split anincident light into polarized components. Therefore, to provide an imagehaving a required contrast, the illuminator has to be used incombination with an absorbing polarizer (where one of the polarizedcomponents is allowed to pass through while the other polarizedcomponent is absorbed). Thus, it is difficult to utilize light with animproved efficiency.

[0027] [Problems of the polarized component separator using thecholesteric liquid crystal polymer-made circular polarizer]

[0028] The illuminators shown in FIG. 3, disclosed in the aforementionedJapanese Patent Gazette No. 2,509,372 and Japanese Published UnexaminedApplication No. 281814 of 1994, respectively, are not always effectiveas expected when it is built in the form of a combination of a dischargelamp used as a light source in practice and a reflector or when it isused to illuminate the modulator.

[0029] More specifically, as shown in FIG. 4, the reflector 111 usedwith the discharge lamp has the actual sectional form of a paraboloid ofrevolution or an ellipsoid of revolution, and so a light beam reflectedby a polarized component splitter formed from the cholesteric liquidcrystal polymer layer 115 towards the light source 101 will be reflectedtwice by the reflector 111. On the assumption that the light beam has aphase change of 180 deg. when it is reflected once by the reflector 111,the phase change of 180 deg. given to the light beam reflected once willbe canceled, namely, the light beam once reflected will have no phasechange, when it is reflected once again.

[0030] Further, since the P- and S-polarized components of light arereflected with one reflectance and another, respectively, by thereflector 111 and they are changed in phase and scattered when they passthrough the glass tube of the discharge lamp as the light source 101, sothe polarized-state conversion will be less effective. Also, when thereflector is a parabolic mirror, a light beam emitted from the focalpoint will return to that point after it is reflected by a reflectingpolarizer, but a light beam emitted from other than the focal point willnot always return to that point after it is reflected by the reflectingpolarizer.

[0031] Also, as shown in FIG. 5, when a spheroidal mirror is used as thereflector 111, the reflected light from the cholesteric liquid crystalpolymer layer 115 will not return, to the point of light emission of thelight source 101 but will be absorbed by the electrodes of the dischargelamp and have the angular distribution thereof spread after it isreflected by the reflector 111, which depends upon the position of thecholesteric liquid crystal polymer layer 115. The spread angulardistribution will increase the Etendue of the light source, which willcause the efficiency of light utilization to be lower.

[0032] As above, the polarized-state converter in the conventionalilluminator is disadvantageous in efficiency of light utilization andmanufacturing cost, and cannot return light to the light source with anyadequate efficiency.

SUMMARY OF THE INVENTION

[0033] It is therefore an object of the present invention to overcomethe above-mentioned drawbacks of the prior art by providing an imagedisplay apparatus including a non-luminous modulator, illuminator toilluminate the optical modulator and a projection lens, and which issimply constructed, thus easy to produce and can utilize light with animproved efficiency.

[0034] The above object can be attained by providing a projection-typeimage display apparatus having an illuminator with a light source,optical modulator illuminated by light from the illuminator and whichmakes spatial modulation of the illumination light according to ato-be-displayed image for either transmission or reflection, and aprojection lens to form the modulated light from the optical modulatorinto an image, the apparatus including:

[0035] a first reflecting element to reflect, towards the light source,unwanted one of a light beam emitted from the illuminator and that willnot illuminate the optical modulator; and

[0036] a second reflecting element to guide, by reflecting, the unwantedlight once reflected by the first reflecting element to the opticalmodulator.

[0037] In the above image display apparatus, the unwanted light isreflected back to the light source by the first and second reflectingelements and also guided to the optical modulator, whereby the lightemitted from the light source can be utilized with an improvedefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] These objects and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments of the present invention whentaken in conjunction with the accompanying drawings, in which:

[0039]FIG. 1 is an axial-sectional view of the conventional imagedisplay apparatus;

[0040]FIG. 2 is a perspective view of a P-S converter used in theconventional image display apparatus in FIG. 1;

[0041]FIG. 3 is an axial-sectional view of a first example of theilluminator used in the conventional image display apparatus in FIG. 1;

[0042]FIG. 4 is an axial-sectional view of a second example of theilluminator used in the conventional image display apparatus in FIG. 1;

[0043]FIG. 5 is also an axial-sectional view of a third example of theilluminator used in the conventional image display apparatus in FIG. 1;

[0044]FIG. 6 is a schematic block diagram of the projection-type imagedisplay apparatus according to the present invention;

[0045]FIG. 7 is a side elevation of the illuminator included in theimage display apparatus shown in FIG. 6, showing the basic optical pathin the illuminator;

[0046]FIG. 8 is a side elevation of the illuminator included in theimage display apparatus in FIG. 6, showing the optical path in theilluminator in which the reflecting element is laid obliquely inrelation to the basic optical path;

[0047]FIG. 9 is a side elevation of the illuminator included in theimage display apparatus in FIG. 6, showing the optical path in theilluminator in which the optic axis of a part of the optical system isshifted from the basic optic axis;

[0048]FIG. 10 is a side elevation of the optical system in the imagedisplay apparatus in FIG. 6, in which the optic axis of a part of theoptical system is shifted from the basic optic axis;

[0049]FIG. 11 is an axial-sectional view of a first embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0050]FIG. 12 is an axial-sectional view of a second embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0051]FIG. 13 is an axial-sectional view of a third embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0052]FIG. 14 is an axial-sectional view of a fourth embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0053]FIG. 15 is an axial-sectional view of a fifth embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0054]FIG. 16 is an axial-sectional view of a sixth embodiment of thelight source included in the image display apparatus shown in FIG. 6;

[0055]FIG. 17 is a front view of the quarter-wave (λ/4) plate includedin the light source shown in FIG. 16;

[0056]FIG. 18 is an axial-sectional view of a first embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0057]FIG. 19 is an axial-sectional view of the light source included inthe image display apparatus in FIG. 6, in which a problem has arisen;

[0058]FIG. 20 is a side elevation of the first embodiment of theilluminator included in the image display apparatus in FIG. 6, showingthe optical path in the illuminator;

[0059]FIG. 21 is an axial-sectional view of a second embodiment of theilluminator included in the image display apparatus in FIG. 6, showingthe optical path in the illuminator;

[0060]FIG. 22 is a front view of the reflecting element in the secondembodiment of the illuminator included in the image display apparatus inFIG. 6;

[0061]FIG. 23 is a front view of the reflecting element in the secondembodiment of the illuminator included in the image display apparatus inFIG. 6, in which the reflecting element is provided obliquely in thelateral direction in the illuminator, showing when the recycling lighthas returned to the reflector FIG. 24 is a front view of the secondembodiment of the illuminator included in the image display apparatus inFIG. 6, in which the reflecting element is laid obliquely in thelongitudinal direction, showing when the recycling light has returned tothe reflector;

[0062]FIG. 25 is an axial-sectional view of a third embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0063]FIG. 26 is an axial-sectional view of a fourth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0064]FIG. 27 is an axial-sectional view of a fifth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0065]FIG. 28A is a perspective view, and FIG. 28B is a plan view, ofthe rod integrator and reflector in the fifth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0066]FIG. 29 is an axial-sectional view of a sixth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0067]FIG. 30A is an axial-sectional view of the first embodiment of theilluminator, and FIG. 30B shows the theory of illumination of theilluminator in FIG. 30A;

[0068]FIG. 31A shows the spectral transmittance of left-hand circularlypolarized light in case the anti-reflection coating is formed on thereflecting circular polarizer in the first embodiment of the imagedisplay apparatus according to the present invention, FIG. 31B shows thespectral transmittance of right-hand circularly polarized light in casethe anti-reflection coating is formed on the reflecting circularpolarizer, FIG. 31C shows the spectral transmittance of left-handcircularly polarized light in case the anti-reflection coating is notformed on the reflecting circular polarizer, and FIG. 31D shows thespectral transmittance of right-hand circularly polarized light in casethe anti-reflection coating is not formed on the reflecting circularpolarizer;

[0069]FIG. 32 is an axial-sectional view of the second embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0070]FIG. 33A is an axial-sectional view of the third embodiment of theilluminator included in the image display apparatus in FIG. 6, and FIG.33B shows the theory of illumination of the illuminator in FIG. 33A;

[0071]FIG. 34A is an axial-sectional view of the fourth embodiment ofthe illuminator included in the image display apparatus in FIG. 6, andFIG. 34B shows the theory of the illuminator in FIG. 34A;

[0072]FIG. 35A is an axial-sectional view of the fifth embodiment of theilluminator included in the image display apparatus in FIG. 6, and FIG.35B shows the theory of illumination of the illuminator in FIG. 35A;

[0073]FIG. 36 is an axial-sectional view of the sixth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0074]FIG. 37A is an axial-sectional view of a seventh embodiment of theilluminator included in the image display apparatus in FIG. 6, and FIG.33B shows the theory of illumination of the illuminator in FIG. 37A;

[0075]FIG. 38 is an axial-sectional view of the seventh embodiment ofthe illuminator included in the image display apparatus in FIG. 6;

[0076]FIG. 39 is an axial-sectional view of the optical modulator in theseventh embodiment of the illuminator included in the image displayapparatus in FIG. 6, showing the principal part thereof;

[0077]FIG. 40 is an axial-sectional view of an eighth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0078]FIG. 41 is an axial-sectional view of the optical modulator in theeighth embodiment of the illuminator included in the image displayapparatus in FIG. 6, showing the principal part thereof;

[0079]FIG. 42 is a side elevation of the optical modulator in the eighthembodiment of the illuminator included in the image display apparatusshown in FIG. 6, showing the configuration of one pixel area thereof;

[0080]FIG. 43 is an axial-sectional view of a ninth embodiment of theilluminator included in the image display apparatus in FIG. 6;

[0081]FIG. 44A is an axial-sectional view of a tenth embodiment of theilluminator included in the image display apparatus in FIG. 6, and FIG.44B shows the principle of the illuminator in FIG. 44A;

[0082]FIG. 45A is an axial-sectional view of an eleventh embodiment ofthe illuminator included in the image display apparatus in FIG. 6, andFIG. 45B shows the principle of the illuminator in FIG. 45A;

[0083]FIG. 46 graphically shows the variation in peak intensity of adisplayed image in an eleventh embodiment of the illuminator included inthe image display apparatus in FIG. 36;

[0084]FIG. 47 is an axial-sectional view of a twelfth embodiment of theilluminator in the image display apparatus in FIG. 6;

[0085]FIG. 48 is an axial-sectional view of a thirteenth embodiment ofthe illuminator included in the image display apparatus in FIG. 6; and

[0086]FIG. 49 is an axial-sectional view of the optical modulator ineach of the eleventh and twelfth embodiments of the illuminator,respectively, included in the image display apparatus in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0087] Note that through the accompanying drawings, like parts areindicated with corresponding references.

[0088] [General-purpose illuminator]

[0089] Referring now to FIG. 6, there is schematically illustrated inthe form of a block diagram the projection-type image display apparatusaccording to the present invention. The image display apparatus shown inFIG. 6 includes a general-purpose illuminator using an optical modulator(will be referred to simply as “modulator” hereunder) which modulates apolarized state of an incident light. As shown, the basic illuminatorincludes a light source 1, integrator 2, polarized-state converter 3,condenser lens group 4, and a modulator 5. Illumination light emittedfrom the illuminator is incident upon the modulator 5. Also, in somecases, there is provided a color separator between the polarized-stateconverter 3 and modulator 5 correspondingly to the modulator 5 fordisplay of an image in three primary colors (R, G and B).

[0090] The integrator 2 is provided to uniform the light intensitydistribution within the light beam emitted from the light source 1. Thepolarized-state converter 3 splits the light beam emitted from the lightsource 1 into polarized components and recombines the thus splitpolarized components. The condenser lens group 4 is provided toilluminate the modulator 5 efficiently by the light beam from theintegrator 3. That is, the condenser lens group 4 forms the light fromthe integrator 2 into an image on the modulator 5.

[0091] [Outline of the image display apparatus according to the presentinvention]

[0092] According to the present invention, the image display apparatusfurther includes a first reflecting element provided to reflect theunwanted light of the light beam emitted from the light source 1, notilluminating the modulator 5, towards the light source 1, and a secondreflecting element provided to reflect the light beam once reflected bythe first reflecting element toward the modulator 5. Since thesereflecting elements permit to reuse the unwanted light as illuminationlight, so they permit to display an image more brightly without havingto increase the light-emission power of the light source 1 itself.

[0093] The above-mentioned illuminator permitting to reuse the unwantedlight as illumination light will be referred to as “recycle-typeilluminator” hereunder. According to the present invention, thefollowing image display apparatuses can be build using the “recycle-typeilluminator”:

[0094] (1) Image display apparatus with polarizing recycle-typeilluminator

[0095] (2) Image display apparatus with illuminator capable ofeffectively improving numerical aperture of modulator

[0096] (3) High-efficiency single-plate color image display apparatus

[0097] (4) High-efficiency sequential color image display apparatus

[0098] (5) Image display apparatus with improved peak brightness

[0099] [Basic type of recycle-type illuminator]

[0100] As shown in FIG. 7, the recycle-type illuminator includes anillumination optical system consisting of the light source 1, integrator2, polarized-state converter (not shown) and the condenser lens group 4,and also a first reflecting element 6. In this illuminator, the lightsource 1 is a discharge lamp provided with a parabolic mirror 7 which isa reflecting mirror 7 having the sectional form of a paraboloid ofrevolution. The light-emission point of the discharge lamp is laid atthe focal point of the parabolic mirror 7. The integrator 2 is a fly-eyeintegrator which is a combination of a first fly-eye lens 8 and secondfly-eye lens 9. The integrator 2 is followed by the polarized-stateconverter (not shown). The condenser lens group 4 consists of acondenser lens 10 and field lens 11. The first reflecting element 6 isshown as a plane mirror laid perpendicularly to the optic axis of theilluminator.

[0101] Note that in the following description, the light beam travelingfrom the light source 1 to the first reflecting element 6 will bereferred to as “primary light” while the light beam having beenreflected by the first reflecting element 6 will be referred to as“recycled light”. In FIG. 7, the typical rays of the primary light areindicated with solid lines, and the recycled light corresponding to theprimary light is indicated with a dashed line.

[0102] More specifically, the primary light emitted from the point oflight emission of the discharge lamp is laid at the focal point of theparabolic mirror 7, and the primary light emitted from thelight-emission point is reflected by the parabolic mirror 7 to be acollimated beam which will be perpendicularly incident upon the firstfly-eye lens 8 of the fly-eye integrator. Then, the primary light isconverged by each of segments of the first fly-eye lens 8 and condensedonto each of segments of the second fly-eye lens 9. That is, thelight-source image carried by the primary light is formed on each of thesegments of the second fly-eye lens 9. The primary light reaches thefirst reflecting element 6 through the second fly-eye lens 9 andcondenser lens group 4. In this illumination optical system, the centralrays of light are parallel to the optic axis, namely, perpendicular tothe first reflecting element 6. That is, the illumination optical systemis a telecentric optical system.

[0103] It should be reminded that each of the segments of the firstfly-eye lens 8 is conjugate with the first reflecting element 6 and thesecond fly-eye lens 9 is conjugate with the light-emission point of thelight source 1. That is, each of the segments of the first fly-eye lens8 works as a diaphragm.

[0104] The recycled light reflected by the first reflecting element 6returns to the fly-eye integrator. Of the recycled light, a light beampassed through a zone of the second fly-eye lens 9 within which theprimary light has passed and that has also passed through thecorresponding first fly-eye lens 8, will be focused at the point oflight emission.

[0105] Note that since actually the parabolic mirror 7 is limited insize and a glass bulb forming the light source 1 will shade the lightbeam, the recycled light will be shaded in the process of returning tothe point of light emission.

[0106] [Illuminator permitting to recycle light with improvedefficiency]

[0107]FIG. 8 is a side elevation of the illuminator included in theimage display apparatus according to the present invention. As shown,the first reflecting element 6 is laid obliquely in relation to theoptic axis of the illuminator, and a reflector 14 is provided as asecond reflecting element, whereby the illumination light can berecycled with an improved efficiency. The illuminator includes anillumination optical system consisting of the light source 1, integrator2, polarized-state converter (not shown) and the condenser lens group 4,and also the first reflecting element 6. In this illuminator, the lightsource 1 is a discharge lamp provided with a spheroidal mirror 16 havingthe sectional form of an ellipsoid of revolution, and its light-emissionpoint is at the focal point of the spheroidal mirror 16. The condenserlens group 4 is an assembly of two lenses: condenser lens (relay lens)10 and field lens 11.

[0108] The reflector 14 serving also as a diaphragm is laid at thesecond focal point of the spheroidal mirror 16. The reflector 14 isformed from a highly reflective material, and has a pattern of aperturescorresponding to rays of light going out of segments, respectively, ofthe second fly-eye lens 9 of the second integrator 2.

[0109] The image-side focal point of the condenser lens 10 is set nearthe field lens 11. In this illumination optical system, the central rayof light is parallel to the optic axis, namely, perpendicular to thefirst reflecting element 6. That is, the illumination optical system isa telecentric optical system. Since the first reflecting element 6 islaid obliquely in relation to the optic axis of the illumination opticalsystem, the recycled light reflected by the first reflecting element 6returns to a position off the aperture pattern of the reflector 14 whichwill reflect the reflected recycled light. The recycled light thusreflected by the reflector 14 returns to the first reflecting element 6.In FIG. 8, the typical rays of the primary light are indicated withsolid lines, and the path of the recycled light corresponding to theprimary light is indicated with a dashed line.

[0110] Also, the illuminator may be constructed with the optic axis ofthe optical system laid downstream of the condenser lens 10 beingshifted an appropriate distance as shown in FIG. 9. The appropriatedistance of the optic axis shift is nearly a quarter of the pitchbetween the segments of the fly-eye integrator 2. Also in FIG. 9, thetypical rays of the primary light are indicated with solid lines, andthe path of the recycled light corresponding to the primary light isindicated with a dashed line.

[0111] In the illuminators shown in FIGS. 8 and 9, respectively, thediameter of the aperture of the reflector 14 generally depends upon theEtendue of an object to be illuminated by light from the illuminated,but it is determined taking in consideration the aspect ratio of theto-be-illuminated object and efficiency of light recycling.

[0112] Also, the second fly-eye lens 9 and reflector 14 are positionedto be generally conjugate with each other. That is, the recycled lightreflected by the first reflecting element 6 defines, on the secondfly-eye lens 9, a light intensity distribution different from thatformed by the primary light, and the illumination pattern of eachsegment of the second fly-eye lens 9 is superposed on the reflector 14.For example, when the segments of the second fly-eye lens 9 have thesame rectangular shape, the illumination pattern formed by the recycledlight on the reflector 14 will be a rectangular one in which theillumination of the central aperture corresponding to each of thesegments is low.

[0113] Also, the pattern of the reflected light from the firstreflecting element 6 results in similar patterns on the segments of thefirst fly-eye lens 8. When the image-side focal point of the firstfly-eye lens 8 is coincident with that of the condenser lens group 4,the reflected light from the first reflecting element 6 returns to aposition symmetric with the coincident position with respect to theoptic axis after reaching the first fly-eye lens 8. In case the firstfly-eye lens 8 is laid symmetrically with respect to the optic axis, thesymmetric pattern of the reflected light pattern will be formed on eachof the segments of the first fly-eye lens 8, with the result that thefirst reflecting element 6 is illuminated with the illumination beingnot uniformed. To uniform the illumination, the field lens 11 and firstfly-eye lens 8 should be spaced from each other. Since the rays of lightother than the central one are not symmetric at the first fly-eye lens8, so the illumination of the recycled light can be uniformed.

[0114] The illuminator may be composed of the light source 1 with aspheroidal mirror 16, relay lens 20 laid at the second focal point ofthe spheroidal mirror 16, reflector 14 laid near the relay lens 20,field lens 21, reflecting polarizer 19, fly-eye integrator 2, condenserlens 10, field lens 11 and the first reflecting element 6 in this orderas shown in FIG. 10. In this case, the optic axis of the optical systemlaid downstream of the condenser lens 10 can be shifted in parallel tothe basic optic axis.

[0115] The reflector 14 is open at the center thereof. Namely, it worksas a diaphragm for the relay lens 20.

[0116] In this illuminator, the recycled light reflected by thereflecting polarizer 19 passes through the field lens 21, relay lens 10and spheroidal mirror 16 and returns to the light-emission point of thelight source 1. The recycled light reflected by the first reflectingelement 6 is reflected by the reflector 14 and returns to the firstreflecting element 6. Also in FIG. 10, the typical rays of the primarylight are indicated with solid lines and the path of the recycled lightcorresponding to the primary light is indicated with a dashed line.

[0117] [First reflecting element]

[0118] The first reflecting element has not to be any dedicated element.An element usable to reflect unwanted light for any other purpose may beemployed as the first reflecting element. Namely, the first reflectingelement may be any one of a reflecting polarizer, polarization beamsplitter, shading layer, reflecting layer of a reflecting modulator,reflective color filter or the like. It will be described later where itshould be positioned.

[0119] [Requirements for improvement of recycling efficiency]

[0120] The requirements for improvement of the efficiency of recyclingthe illumination light includes the following four:

[0121] (1) The first reflecting element and integrator should beoptically conjugate with each other.

[0122] (2) The illuminator components should reflect as little aspossible at the surfaces thereof.

[0123] (3) The illuminator should be constructed to efficiently reflectthe return light.

[0124] (4) The Etendue of the modulator should be so large as to allowthe light source Etendue to increase in the process of light recycling.

[0125] The first requirement is as having previously been described.

[0126] To meet the above second requirement, it is necessary to form ananti-reflection coating on each optical component and minimize thereflecting surface by integrally forming parts which could be formedintegrally with each other. For example, the discharge lamp bulb shoulddesirably have such an anti-reflection coating formed on the glasssurface thereof. Also, the P-S converter, condenser lens 10 and secondfly-eye lens 9 of the fly-eye integrator shown in FIG. 7 should be laidoptically close to each other.

[0127] The third requirement will be described later.

[0128] The “Etendue of the modulator” in the fourth requirement isrepresented by a product of an illuminated area of the modulator and asolid angle of the illumination light, and the “Etendue of the lightsource” is represented by a product of an area of light emission and asolid angle of the light emission. For example, in a light sourceconsisting of a parabolic mirror and discharge lamp bulb, the “Etendueof the light source” is a product of an opening area of the parabolicmirror and an emission solid angle of the outgoing light at the openingof the parabolic mirror. The Etendue of the modulator will increase asthe unwanted light is returned to the light source and reflected backtowards the modulator. In case the Etendue of the modulator is smallerthan that of the light source, the recycled light will illuminate a zonelarger than a one intended to be illuminated and the efficiency ofrecycling will be smaller.

[0129] [Construction of the light source for improved efficiency ofrecycling (1)]

[0130] Generally, in case the light source is provided with theparabolic mirror as above, the recycled light will not preciselycoincide in position and angle with the primary light when the unwantedlight returns to the opening of the parabolic mirror. Also, when theoptical elements have been misaligned with each other in the process ofmanufacturing, the recycled light will not return to the light-emissionpoint of the light source. The light source improved in these respectsis shown in FIG. 11 which is an axial-sectional view of the firstembodiment of the light source included in the image display apparatusaccording to the present invention. As shown, the light source with theparabolic mirror 7 additionally includes a protective glass (face plate)13 provided at the open end of the mirror 7 and having reflectors 14 aand 14 b provided as the second reflecting element on the front side 13b or rear side 13 a thereof. The reflectors 14 a and 14 b are positionedat the center and along the periphery, respectively, of the protectiveglass 13. Each of them may be a thin film or dielectric multilayer filmof a metallic material such as aluminum, silver or the like formed onthe protective glass 13. Alternatively, they may be reflectors separatefrom the protective glass 13 and located in the vicinity of the latter.

[0131] Note that the light-emission point is within the lamp bulb 12(glass tube) having an anti-reflection coating 15 formed on the surfaceof the glass tube thereof.

[0132] Generally, in the light source consisting of the parabolic mirror7 and lamp bulb 12, the entire open end of the parabolic mirror 7 is noteffective as the light source but the center and periphery of the lampbulb 12 are ineffective zones where the illumination light reflected bythe parabolic mirror 7 will not be transmitted, as shown in FIG. 12.Namely, the reflectors 14 a and 14 b are provided in such ineffectivezones.

[0133] The reflectors 14 a and 14 b should desirably be formed as closeto the light-emission point of the light source as possible because alarger part of the recycled light will be shaded by the glass tube ofthe lamp bulb 12 if the reflectors 14 a and 14 b are apart from thelight-emission point as shown in FIG. 12. To avoid this, the reflectors14 a and 14 b should more desirably be positioned closer to thelight-emission point, by forming them on the rear side 13 a of theprotective glass 13, than formed on the front side 13 b of theprotective glass 13, as shown in FIG. 13. Also, the reflectors 14 a and14 b should desirably be positioned closer to the effective zone of theparabolic mirror 7. When the reflectors 14 a and 14 b are far from theeffective zone of the parabolic mirror 7, the unwanted primary light(light emitted directly from the light-emission point) cannot be shadedsufficiently and thus a larger part of the reflected light to bereturned towards the light source will be reflected.

[0134] Also note that the reflector 14 b formed along the periphery ofthe protective glass 13 may be laid obliquely at an appropriate anglewith the optic axis as shown in FIG. 14. That is, in this case, thereflector 14 b is formed to be a part of a conical or spherical surface.In case the reflector 14 b is not laid so obliquely, the light beamreflected by the reflector 14 b will be incident upon a large radialzone of the first fly-eye lens 8. By positioning the reflector 14 bobliquely in relation to the optic axis, it is possible to prevent thelight beam reflected by the reflector 14 b from diverging through thefirst fly-eye lens 8. It should be noted that the oblique angle of thereflector 14 b depends upon the relation in magnitude between the focaldistance of the parabolic mirror 7 and size of the light-emission point.

[0135] [Construction of the light source for improved efficiency ofrecycling (2)]

[0136] Also in case the light source is composed of the lamp bulb 12,spheroidal mirror 16 which replaces the aforementioned parabolic mirror,and the protective glass 13, the reflectors 14 a and 14 b are formed onthe protective glass 13 and in an ineffective zone where the primarylight is not allowed to pass through, as shown in FIG. 15 which is anaxial-sectional view of a fifth embodiment of the light source includedin the image display apparatus according to the present invention. Thatis, the reflector 14 a and 14 b are formed at the center and along theperiphery, respectively, of the protective glass 13.

[0137] Different from the parabolic mirror, however, it is notsufficient for improvement of the efficiency of light recycling to formthe reflectors 14 a and 14 b solely on the spheroidal mirror 16. Thereason is that since the light-emission point of the light source ispositioned at the first focal point of the spheroidal mirror 16, solight (primary light) emitted from the light-emission point will befocused at the second focal point of the spheroidal mirror 16. Thus, torecycle the light effectively and efficiently, it is necessary to focusthe light beam reflected by the reflectors at the second focal point ofthe spheroidal mirror 16. To this end, condenser lenses 17 a and 17 bare provided in close proximity to the reflectors 14 a and 14 b,respectively. The condenser lenses 17 a and 17 b are a circular lens anda toroidal lens, respectively, corresponding to the reflectors 14 a and14 b, respectively. The circular lens is positioned at the center of theprotective glass 13 while the toroidal lens is positioned along theperiphery of the protective lens 13. Their focal points are coincidentwith the second focal point of the spheroidal mirror 16. The recycledlight caused by the condenser lenses 17 a and 17 b to pass through thesecond focal point of the spheroidal mirror 16 becomes telecentric atthe first reflecting element as having previously been described.Therefore, the recycled light reflected by the first reflecting elementreturns to the second focal point of the spheroidal mirror 16 andthereafter it becomes an effective light beam.

[0138] [Construction of the light source for improved efficiency ofrecycling (3)]

[0139] Referring now to FIG. 16, there is schematically illustrated inthe form of an axial-sectional view the sixth embodiment of the lightsource included in the image display apparatus according to the presentinvention. As shown, the light source may be composed of the lamp bulb12 with the parabolic mirror 7, a quarter-wave (λ/4) plate 18, and areflecting circular polarizer 19. As above, the phase change in thelight reflection by the parabolic mirror 7 is not always 180 deg. but itwill also vary depending upon the incident angle or wavelength. Toaccommodate this fact, the quarter-wave plate 18 and reflecting circularpolarizer 19 are used in this light source to make a P- orS-polarization of the light in relation to the parabolic mirror 7. Thequarter-wave plate 18 is divided into plural (an even number of) radialzones 18 a, 18 b, 18 c, 18 d, 18 a′, 18 b′, 18 c′ and 18 d′ symmetricwith each other with respect to the center axis of the parabolic mirror7 as shown in FIG. 17. The phase-retardation axis of each of theseradial zones forms an angle of 45 deg. with a straight line connectingthe center of each radial zone and the center axis of the parabolicmirror 7, and is perpendicular to the phase-retardation axis of theradial zones which are symmetric with respect to the center axis of theparabolic mirror 7. It should be noted that an ultraviolet- andinfrared-cut filter (not shown) is provided between the quarter-waveplate 18 and protective glass 13 of the lamp bulb 12.

[0140] The reflecting circular polarizer 19 may be a one formed from acholesteric liquid crystal polymer. The quarter-wave plate 18 shoulddesirably be a one which works in a wide-band domain of wavelength. Itshould be noted that an anti-reflection coating is applied on thesurface of contact with air.

[0141] The outgoing light from the lamp bulb 12 is linearly polarized bythe quarter-wave plate 18 when it passes through the latter, and reachesthe reflecting circular polarizer 19. At this time, the light will be P-or S-polarized in relation to the incident surface of the reflectingcircular polarizer 19. Thus, the polarized light in one direction isreflected by the reflecting circular polarizer 19 towards the lightsource.

[0142] The reflected light from the reflecting circular polarizer 19 ispassed through the quarter-wave plate 18, reflected twice by theparabolic mirror 7, and then reaches the quarter-wave plate 18 again. Atthis time, the light is incident upon a zone (18 a′, for example) of thequarter-wave plate 18, symmetric with a zone (18 a, for example) of thesame plate 18, through which the light has passed when reflected by thereflecting circular polarizer 19, with respect to the center axis of theparabolic mirror 7. Then, since the light has already passed through thequarter-wave plate 18 and reflecting circular polarizer 19, it is P- orS-polarized without incurring any phase difference. Therefore, passedthrough the zone of the quarter-wave plate 18, orthogonal to thephase-retardation axis, the light is circularly polarized in a directionopposite to that in which it has initially been incident upon thereflecting circular polarizer 19, and thus passes through the reflectingcircular polarizer 19. In the light source, the polarized state ischanged or converted in this way.

[0143] Note that in the light source shown in FIG. 16, the quarter-waveplate 18 and reflecting circular polarizer 19 are formed integrally withthe protective glass 13 formed integrally with the parabolic mirror 7,but they may be formed separately from the protective glass 13.

[0144] However, the quarter-wave plate 18 should desirably be laid asclose to the parabolic mirror 7 as possible. If it is laid apart fromthe parabolic mirror 7, a light beam having a large angle with the opticaxis, having been reflected twice by the parabolic mirror 7 and reachedthe quarter-wave plate 18 again, will not be more likely to pass throughthe symmetric zones of the quarter-wave plate 18.

[0145] Also, the more the reflecting circular polarizer 19 is apart fromthe parabolic mirror 7, the reflected light from the reflecting circularpolarizer 19 will be more likely to reach the reflector 14 b at theperiphery. In this case, the reflected light will not pass through thequarter-wave plate 18 but will be incident as a circularly polarizedlight upon the reflector 14 b. When the light is reflected by thereflector 14 b, its phase is changed by 180 deg. to provide anopposite-directional circularly polarized light which will pass throughthe reflecting circular polarizer 19. In this case, since the light isnot reflected by the parabolic mirror 7 or influenced in any way by thelamp bulb 12, so the illumination light will possibly be recycled withan improved efficiency.

[0146] Note that similarly to the aforementioned combination of thequarter-wave plate and circular polarizer, a combination of a half-waveplate and a reflecting linear polarizer may provide a light source whichcan work similarly to the aforementioned light source.

[0147] [Construction of the light source for improved efficiency ofrecycling (4)]

[0148] Referring now to FIG. 18, there is schematically illustrated inthe form of an axial-sectional view the first embodiment of theilluminator included in the image display apparatus according to thepresent invention. As shown, the light source may be composed of thelamp bulb 12 with the spheroidal mirror 16, quarter-wave plate 18, relaylens 20, field lens 21 and reflecting circular polarizer 19.

[0149] In case of the light source with the parabolic mirror 7 as shownin FIG. 19, the light beam off the focal point of the parabolic mirror7, reflected by the reflecting circular polarizer 19 and incident againupon the lamp bulb 12, will possibly be shaded by a shade such as theelectrode of the lamp bulb 12. To avoid this possibility in the lightsource with the spheroidal mirror 16, the light-emission point of thelamp bulb 12 is located at the first focal point of the spheroidalmirror 16, the relay lens 20 is located at the second focal point of thespheroidal mirror 16, and the reflecting circular polarizer 19 islocated nearly at a point of conjugation with the reflecting point onthe spheroidal mirror 16 and relay lens 20, as shown in FIG. 20. Theincident light upon the reflecting circular polarizer 19 is settelecentric by the field lens 21.

[0150] The light beam reflected by the reflecting circular polarizer 19is reflected by the spheroidal mirror 16 back to the position at whichthe primary light has been reflected. The reflected light from thespheroidal mirror 16 returns to a position symmetric with thelight-emission point with respect to the first focal point of thespheroidal mirror 16. Namely, the light beam is less shaded by thedischarge electrode of the lamp bulb 12 or the like.

[0151] As in the aforementioned “Construction of the light source forimproved efficiency of recycling (3)”, the quarter-wave plate 18 isdivided into plural radial zones different in direction ofphase-retardation axis from each other as shown in FIG. 17, and it islaid in the vicinity of the protective glass 13 as shown in FIG. 18.Even when disposed between the reflecting circular polarizer 19 andfield lens 21, the quarter-wave plate 18 will provide the same effect asabove.

[0152] The quarter-wave plate 18 should desirably be a one which canwork in a wide-band domain of wavelength. Also, an ultraviolet- andinfrared-cut filter (not shown) is provided between the quarter-waveplate 18 and protective glass 13 of the lamp bulb 12.

[0153] Referring now to FIG. 21, there is schematically illustrated inthe form of an axial-sectional view the second embodiment of theilluminator included in the image display apparatus according to thepresent invention. As shown, the reflecting circular polarizer 19 may bea one made of a cholesteric liquid crystal polymer. It should be notedthat an anti-reflection coating 23 is applied on the air-contactsurface.

[0154] The outgoing light from the lamp bulb 12 is linearly polarized bythe quarter-wave plate 18 when it passes through the latter, and isincident upon the reflecting circular polarizer 19. At this time, thelight will be P- or S-polarized in relation to the incident surface ofthe reflecting circular polarizer 19. Thus, the polarized light in onedirection is reflected by the reflecting circular polarizer 19 towardsthe light source.

[0155] The reflected light from the reflecting circular polarizer 19 ispassed through the quarter-wave plate 18, reflected twice by thespheroidal mirror 16, and then incident again upon the quarter-waveplate 18. At this time, the light is incident upon a zone (18 a′, forexample) of the quarter-wave plate 18 symmetric with a zone (18 a, forexample) of the same plate 18, through which the light has passed whenreflected by the reflecting circular polarizer 19, with respect to thecenter axis of the parabolic mirror 7. Then, since the light has alreadypassed through the quarter-wave plate 18 and reflecting circularpolarizer 19, it is P- or S-polarized without incurring any phasedifference. Therefore, passing through the zone of the quarter-waveplate 18, orthogonal to the phase-retardation axis, the light iscircularly polarized in a direction opposite to that in which it hasinitially been incident upon the reflecting circular polarizer 19, andpasses through the latter. Thus, the polarized state is converted in thelight source.

[0156] Note that similarly to the aforementioned combination of thequarter-wave plate and circular polarizer, a combination of a half-waveplate and a reflecting linear polarizer may provide a light source whichcan work similarly to the aforementioned light source.

[0157] [Construction of the illuminator for improved efficiency ofrecycling (1)]

[0158] As shown in FIG. 21, the illuminator used in the image displayapparatus according to the present invention includes the light source24 constructed as having been illustrated and described in theforegoing, fly-eye integrator 2, condenser lens 10, field lens 11, andfirst reflecting element 6. In this illuminator, each of the segments ofthe fly-eye lens 9 of the fly-eye integrator 2 is a diaphragm for eachof segments of the corresponding fly-eye lens 8. Namely, the light beamspassing through the segments of the corresponding second fly-eye lens 9are all focused on an object to be illuminated. Actually, however, notthe entire diaphragm is utilized but the diaphragm has ineffective zoneswhere the illumination is low as shown in FIG. 22. In this illuminator,such ineffective zones on the second fly-eye lens 9 are utilizedeffectively.

[0159] More specifically, the above illuminator has the reflector 14provided, as a second reflecting element, between the second fly-eyelens 9 of the fly-eye integrator 2 and the condenser lens 10. It shouldbe noted that in case the P-S converter exists as above, the reflector14 is provided between the second fly-eye lens 9 of the fly-eyeintegrator 2 and the P-S converter.

[0160] The reflector 14 is disposed where it will not shade the primarylight from the light source. More particularly, the reflector 14 isformed to have an aperture pattern whose configuration corresponds tothe light intensity distribution on the second fly-eye lens 9 of thefly-eye integrator 2 shown in FIG. 22 or to have a stripe structure.

[0161] In this illuminator, the recycled light reflected by the firstreflecting element 6 can be returned again to the to-be-illuminatedobject by returning it to any zone other than the aperture of thereflector 14, and it can thus be utilized efficiently.

[0162] Since the reflector 14 is laid at the side, nearer to thelight-source, of the condenser lens 10, the condenser lens 10 and fieldlens 11 will form together a relay-condenser illumination optical systemfor the recycled light. The condenser lens 10 works as a relay lens.Also, the optical system is a telecentric one for the first reflectingelement 6 and reflector 14. Namely, the central ray of the light beam isparallel to the optic axis of the optical system.

[0163] In case the recycled light reflected by the reflector 14 has beenreflected again by the first reflecting element 6, it retraces theoptical path along which the primary light has traveled and returns tothe light source 24. With this process repeatedly done, the illuminationlight is recycled.

[0164] The first reflecting element 6 is laid obliquely in relation tothe optic axis. The first reflecting element 6 is horizontally orvertically oblique in relation to the optic axis. When the firstreflecting element 6 is horizontally oblique, the light intensitydistribution of the recycled light on the second fly-eye lens 9 of thefly-eye integrator 2 is such that bright zones appear shifted laterallyfrom the aperture pattern of the reflector 14 as indicated with dashedlines in FIG. 23. When the first reflecting element 6 is verticallyoblique, the light intensity distribution of the recycled light on thesecond fly-eye lens 9 of the fly-eye integrator 2 is such that thebright zones appear shifted longitudinally from the aperture pattern ofthe reflector 14 as indicated with dashed lines in FIG. 24.

[0165] A part of the light thus returning to the reflector 14 will beoutside the profile of the second fly-eye lens 9 of the fly-eyeintegrator 2. However, the light returning to the reflector 14 can bewholly collected with the use of the condenser lens 10 having a largeroutside diameter. Also, since a part of the light returning to thereflector 14, overlapping the aperture pattern indicated with solidlines in FIGS. 18 and 19, returns to the light source 24 through theaperture pattern, it will not be lost but will be reused as theillumination light.

[0166] Also, the first reflecting element 6 may not be laid obliquelyrelative to the optic axis but may be shifted along with the condenserlens 11 a predetermined distance in parallel to the optic axis,. Itshould be noted that the predetermined distance of shifting of theoptical system laid downstream of the condenser lens 11 in relation tothe optic axis is about a quarter of the pitch between the fly-eye lenssegments.

[0167] Note that the surface of the reflector 14 should desirably besuperior in flatness for an improved efficiency of recycling theillumination light. However, the recycled light reflected by the firstreflecting element 6, having a pattern which will be defined byinverting the aperture pattern of the reflector 14, returns to thereflector 14. Therefore, for a uniform illumination by the recycledlight, the reflector 14 may have an appropriate light-scatteringsurface.

[0168] Further, the illuminator may include two fly-eye integrators 2and 25 as shown in FIG. 25. In this case, the recycled light can have animproved uniformity of illumination.

[0169] More particularly, the first fly-eye integrator 2 consists ofsegments generally similar to the object to be illuminated. The secondfly-eye integrator 25 laid between the first fly-eye integrator 2 andlight source 24 may be different in shape from the first fly-eyeintegrator 2.

[0170] The second fly-eye integrator 25 forms the relay-condenserillumination optical system in which the reflector 14 as the secondreflecting element is located in a zone near the diaphragm and where itwill not shade the primary light.

[0171] Also, the optic axis of the optical system laid downstream of thecondenser lens 10 (condenser lens 10 and first reflecting element 6) isshifted about a quarter of the pitch between the segments of the firstfly-eye integrator 2 in relation to the optic axis of the other opticalsystem. The first and second fly-eye integrators 2 and 25 are setdifferent in segment pitch from each other.

[0172] In this illuminator, the recycled light reflected by the firstreflecting element 6 forms a reflected-light pattern on each of thesegments of the first fly-eye lens 8 of the first fly-eye integrator 2.Since the second fly-eye integrator 25 is different in segment pitchfrom the first fly-eye integrator 2, the recycled light incident uponthe reflector 14 is reflected by the latter. When the reflected recycledlight is incident again upon the first fly-eye lens 8 of the firstfly-eye integrator 2, it forms a pattern different from that which hasinitially been formed when it returns to the first fly-eye lens 8.Therefore, the recycled light passes through the first fly-eyeintegrator 2, and it incident upon the first reflecting element 6. Atthis time, the recycled light will have the illumination thereofuniformed.

[0173] [Construction of the illuminator for improved efficiency ofrecycling (2)]

[0174] Referring now to FIG. 26, there is schematically illustrated inthe form of an axial-sectional view the fourth embodiment of theilluminator included in the image display apparatus according to thepresent invention. As shown, the illuminator may be constructed with theoptic axis of the optical system (condenser lens 10, field lens 11 andfirst reflecting element 6) laid downstream of the condenser lens 10being shifted in parallel to that of the light source 24. The fly-eyeintegrator 2 is laid between the light source 24 and condenser lens 10in a zone where it will work with both the light source 24 and theoptical system laid downstream of the condenser lens 10. The reflector14 is disposed in a position at the side, nearer to the light source 24,of the fly-eye integrator 2, symmetric with the light source 24 withrespect to the optic axis of the optical system laid downstream of thecondenser lens 10.

[0175] In the above illuminator, a part of the primary light havingreached the first reflecting element 6 from the light source 24 isincident, as a recycled light, upon the reflector 14 disposed at theside, nearer to the light source 24, of the fly-eye integrator 2, anduniformed by the fly-eye integrator 2 to illuminate theto-be-illuminated object with a high efficiency.

[0176] In case the recycled light reflected by the reflector 14 has beenreflected again by the first reflecting element 6, it retraces theoptical path along with the primary light has traveled to return to thelight source 24. With this process repeated, the illumination light isrecycled.

[0177] [Construction of the illuminator for improved efficiency ofrecycling (3)]

[0178] Referring now to FIG. 27, there is schematically illustrated inthe form of an axial-sectional view the fifth embodiment of theilluminator included in the image display apparatus according to thepresent invention. As shown, the illuminator may include a rodintegrator 26. The rod integrator 26 is a prismatic optical device madeof a transparent material. The light beam is incident upon one end ofthe rod integrator 26 and goes out from the other end. This illuminatoris constructed out of a light source 27 with the spheroidal mirror 16,rod integrator 26, and a relay-condenser optical system laid between thelight source 27 and rod integrator 26. The relay-condenser opticalsystem includes a condenser lens 28 and relay lens 29. The condenserlens 28 is located at the second focal point of the spheroidal mirror16, and the relay lens 29 is at the focal point of the condenser lens28.

[0179] The reflector 14 having an aperture formed therein is providednear one end of the rod integrator 26, upon which the light beam from alight source 27 is incident. The reflector 14 may be formed on the endface, nearer to the light source 27, of the rod integrator 26, forexample, as shown in FIGS. 28A and 28B.

[0180] Further, a relay lens system (30, 20), field lens 21 and firstreflecting element 6 are provided at the light-incident end of the rodintegrator 26.

[0181] When the recycled light reflected by the first reflecting element6 returns to the light-incident end of the rod integrator 26, itsillumination has been uniformed by the rod integrator 26. Thus, therecycled light having returned to a part, other than the aperture, ofthe reflector 14 is reflected by the reflector 14. Similarly to theprimary light, the reflected light beam from the reflector 14 isuniformed by the rod integrator 26 to illuminate the to-be-illuminatedobject with a high efficiency. The recycled light passed through theaperture will return to the light source 27. With this processedrepeatedly done, the illumination light is recycled.

[0182] Note that the above light source may be a one with a parabolicmirror.

[0183] [Construction of the illuminator for improved efficiency ofrecycling (4)]

[0184] Referring now to FIG. 29, there is schematically illustrated inthe form of an axial-sectional view the sixth embodiment of theilluminator included in the image display apparatus according to thepresent invention. As shown, the illuminator may be formed with theoptic axis of a part of the optical system laid shifted in parallel tothat of the rest of the optical system. The illuminator further includesthe condenser lens 10 provided between the relay lens 20 and field lens21 in the illuminator having been illustrated and described withreference to FIG. 27, and is formed with the optic axis of the opticalsystem laid downstream of the condenser lens 10 being shifted inparallel to that of the optical system ranging from the light source 27to the relay lens 20. Further, at the side, nearer to the light source,of the condenser lens 10, there is provided a reflector 14 c in aposition symmetric with the optic axis of the optical system laid downto the relay lens 20 with respect to the optic axis of the opticalsystem laid downstream of the condenser lens 10.

[0185] In the above illuminator, the recycled light reflected by thefirst reflecting element 6 is incident upon the reflector 14 c,reflected by the latter, passes through the condenser lens 10 and fieldlens 21, and is incident again upon the first reflecting element 6. Whenthe recycled light reflected again by the first reflecting element 6returns to the rod integrator 26, its illumination has been uniformed bythe rod integrator 26. Thus, the recycled light having returned to thepart, other than the aperture, of the reflector 14 is reflected by thelatter. The light beam reflected by the reflector 14 is uniformed by therod integrator 26 to illuminate the to-be-illuminated object with a highefficiency. The recycled light passed through the aperture returns tothe light source 27. With this process repeatedly done, the illuminationlight is recycled.

[0186] [Construction of the image display apparatus with the function ofpolarized component conversion (1)]

[0187] Referring now to FIG. 30A, there is schematically illustrated inthe form of an axial-sectional view the first embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus according to the present invention includes theaforementioned light source 24. The light source 24 includes the lampbulb 12 and parabolic mirror 7. Also, the image display apparatusincludes the first reflecting element 6 as a reflecting polarizer. Thus,it has a function as a polarized-state converter.

[0188] More specifically, the image display apparatus includes the lightsource 24, fly-eye integrator 2, reflector 14, condenser lens 10, fieldlens 21, reflecting polarizer 6 and a modulator 31, disposed in thisorder at predetermined intervals. The reflecting polarizer 6 is laidobliquely in relation to the optic axis. The angulation of thereflecting polarizer 6 is such that as mentioned above, when therecycled light reflected by the reflecting polarizer 6 returns to thereflector 14, it will be incident mainly upon an ineffective part of thereflector 14, off the aperture patten of the latter.

[0189] The reflecting polarizer 6 may be made of a cholesteric liquidcrystal polymer. Also, by forming an anti-reflection coating on theair-contact surface of a substrate on which the cholesteric liquidcrystal polymer layer is formed, it is possible to improve the polarizedcomponent splitting as shown in FIG. 31. In FIG. 31, it is presumed thatthe range of selective reflection by the cholesteric liquid crystalpolymer layer is set within a range of 420 to 690 nm. FIG. 31A shows thespectral transmittance of left-hand circularly polarized light when theanti-reflection coating is formed on the reflecting circular polarizer,FIG. 31B shows the spectral transmittance of right-hand circularlypolarized light when the anti-reflection coating is formed on thereflecting circular polarizer, FIG. 31C shows the spectral transmittanceof left-hand circularly polarized light when the anti-reflection coatingis not formed on the reflecting circular polarizer, and FIG. 31D showsthe spectral transmittance of right-hand circularly polarized light whenthe anti-reflection coating is not formed on the reflecting circularpolarizer.

[0190] The illumination light emitted from the light source 24 is passedthrough the fly-eye integrator 2, aperture pattern of the reflector 14,condenser lens 10 and field lens 11 to the reflecting polarizer 6. Onecircularly polarized light passes through the reflecting polarizer 6while the other is reflected by the polarizer 6 as shown in FIG. 30B.The reflected circularly polarized light returns to the reflector 14,and is reflected by the latter to be an oppotiste-directional circularlypolarized light. This light is incident again upon the reflectingpolarizer 6 and passes through the latter. The light thus passed throughthe reflecting polarizer 6 is incident upon the modulator 31 where itwill undergo spatial modulation according to an image to be displayed.

[0191] Note that when linearly polarized light has to be incident uponthe modulator 31, a quarter-wave plate should be provided between thereflecting polarizer 6 and modulator 31. Also, by additionally providingan absorbing polarizer, it is possible to shade unwanted polarizedlight.

[0192] Also, the reflecting polarizer may be a reflecting linearpolarizer. In this case, the quarter-wave plate is provided on thereflector 14 or at the side, nearer to the light source, of thereflecting linear polarizer.

[0193] [Construction of the image display apparatus with the function ofpolarized-state conversion (2)]

[0194] Referring now to FIG. 32, there is schematically illustrated inthe form of an axial-sectional view the second embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus may be composed of the light source 24 includingthe lamp bulb 12 and parabolic mirror 7, quarter-wave plate 18, fly-eyeintegrator 2, reflecting polarizer 6, condenser lens 10, field lens 11and modulator 31 provided in this order at predetermined intervals.

[0195] In the above image display apparatus, the reflecting polarizer 6may be made of a cholesteric liquid crystal polymer-made circularpolarizer. Also, the quarter-wave plate 18 is divided into plural (aneven number of) radial zones 18 a, 18 b, 18 c, 18 d, 18 a′, 18 b′, 18 c′and 18 d′ symmetric with each other with respect to the center axis ofthe parabolic mirror 7 as shown in FIG. 17. The phase-retardation axisof each of these radial zones forms an angle of 45 deg. with a straightline connecting the center of each radial zone and the center axis ofthe parabolic mirror 7, and is perpendicular to the phase-retardationaxis of the radial zones which are symmetric with each other withrespect to the center axis of the parabolic mirror 7.

[0196] The light emitted from the light source 24 is passed through thequarter-wave plate 18 to the reflecting polarizer 6. At the reflectingpolarizer 6, one circularly polarized component of the light is allowedto pass through while the other circularly polarized component isreflected towards the light source 24. Since the second fly-eye lens ofthe fly-eye integrator 2 is conjugate with the light emitter (lamp bulb12) of the light source 24, so the reflected light from the reflectingpolarizer 6 returns to the light emitter (lamp bulb 12). Thus, the lightreturning towards the light source 24 is converted to a linearlypolarized light when passing through the quarter-wave plate 18, and thenincident upon the parabolic mirror 7.

[0197] The phase-retardation axis of the quarter-wave plate 18 isdirected at an angle of 45 deg. with a straight line connecting thecenter of each area and the center axis of the parabolic mirror 7, thatis, the incident surface of the parabolic mirror 7. Thus, the linearlypolarized light after returning from the reflecting polarizer 6 andpassing through the quarter-wave plate 18 is P- or S-polarized inrelation to the incident surface of the parabolic mirror 7. The light isreflected twice by the parabolic mirror 7 without incurring any phasechange, and passes through the quarter-wave plate 18 again.

[0198] The light having passed three times through the quarter-waveplate 18 as above will be circularly polarized in a direction in whichit will pass through the reflecting polarizer 6. Thus, the reflectedlight from the reflecting polarizer 6 is recycled, and thus the lightchanged in polarized state after passing through the reflectingpolarizer 6 can be utilized with an improved efficiency.

[0199] [Construction of the image display apparatus with the function ofpolarized-state conversion (3)]

[0200] Referring now to FIG. 33A, there is schematically illustrated inthe form of an axial-sectional view the third embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus is constructed out of an illuminator composed ofthe light source 27 with the spheroidal mirror 16, relay lens 28, fieldlens 29, reflector 14 having an aperture, rod integrator 26, condenserlens 30, relay lens 20, reflector 14 c, condenser lens 10, field lens 21and the reflecting polarizer 6, and also the modulator 31 provided inaddition to the illuminator. The optic axis of the optical system laiddownstream of the condenser lens 10 is shifted in parallel to that ofthe optical system ranging from the light source 27 to the relay lens20. In this image display apparatus, the light source 27 and reflectingpolarizer 6 provide the function of polarized-state conversion. As inthe aforementioned embodiment, the reflecting polarizer 6 is made of acholesteric liquid crystal polymer-made circular polarizer.

[0201] The illumination light emitted from the light source 27 is passedthrough the relay lens 28, field lens 29, rod integrator 26, condenserlens 30, relay lens 20, condenser lens 10 and field lens 21 to thereflecting polarizer 6 which allows one circularly polarized componentto pass through it while reflecting the other circularly polarizedcomponent, as shown in FIG. 33B. The reflected polarized light isincident upon the reflector 14 c. The light is reflected by thereflector 14 c to be an opposite-directional circularly polarized light.This light is incident again upon the reflecting polarizer 6 and passesthrough the latter. The light thus passed through the reflectingpolarizer 6 is incident upon the modulator 31 in which it will undergospatial modulation according to an image to be displayed.

[0202] Note that when a linearly polarized light has to be incident uponthe modulator 31, a quarter-wave plate should be provided between thereflecting polarizer 6 and modulator 31. Also, by additionally providingan absorbing polarizer, it is possible to cut off unwanted polarizedlight.

[0203] Also, the reflecting polarizer may be a reflecting linearpolarizer. In this case, the quarter-wave plate is provided on thereflector 14 or at the side, nearer to the light source, of thereflecting linear polarizer.

[0204] [Construction of the image display apparatus with the function ofpolarized-state conversion (4)]

[0205] Referring now to FIGS. 34A, FIG. 35A and 36, there areschematically illustrated in the form of an axial-sectional view thefourth, fifth and sixth embodiments of the image display apparatusaccording to the present invention. As shown, each of the embodiments ofthe image display apparatus includes the light source 27 with thespheroidal mirror 16, relay lens 28, field lens 29, reflector 14 havingan aperture, rod integrator 26, condenser lens 30, relay lens 20,reflector 14 c, condenser lens 10 and the field lens 21, and also themodulator 31 provided at the lateral side of the polarization beamsplitter 32. The optic axis of the optical system laid downstream of thecondenser lens 10 is shifted in parallel to that of the optical systemranging from the light source 27 to the relay lens 20. Also, aquarter-wave plate 34 is provided between the condenser lens 10 andreflector 14 c. In this image display apparatus, the polarization beamsplitter 32 provides the function of polarized-state conversion.

[0206] More specifically, as shown in FIG. 34A, a reflector 33 isprovided downstream of the polarization beam splitter 32 as viewed fromthe field lens 21 and the modulator 31 is provided at the lateral sideof the polarization beam splitter 32 as above. The reflector 33 andmodulator 31 are located to have an equal optical path length from thefield lens 21, namely, from the inner reflecting plane of thepolarization beam splitter 32.

[0207] In the above image display apparatus, the outgoing light from thelight source 27 is passed through the illumination optical system to thepolarization beam splitter 32. The illumination light is split by thepolarization beam splitter 32 into S- and P-polarized light beams. Asshown in FIG. 34B, the S-polarized light is reflected at the reflectingplane of the polarization beam splitter 32 and incident upon themodulator 31, while the P-polarized light is passed through thereflecting plane of the polarization beam splitter 32 and incident uponthe reflector 33 by which it will be reflected. The recycled lightreflected by the reflector 33 retraces the optical path, passes througha quarter-wave plate 34, is reflected by the reflector 14 c, and passesthrough the quarter-wave plate 34 again. The light is S-polarized by thequarter-wave plate 34 and incident again upon the polarization beamsplitter 32. At this time, since the recycled light is S-polarized inrelation to the reflecting plane of the polarization beam splitter 32,it is reflected at the reflecting plane to illuminate the modulator 31to illuminate the modulator 31.

[0208] Note that the optic axis of the optical system laid downstream ofthe condenser lens 10 should desirably be shifted in a direction inwhich the distance between the field lens 21 and polarization beamsplitter 32 will not change as the optic axis is shifted, as shown inFIG. 34C, in order to allow the angle of incidence of the light beam toincrease correspondingly to an optic axis movement. Also, owing to thisconstruction, the peak brightness which will be described in detaillater can be effectively improved.

[0209] In case an intended optical extinction ratio cannot be attainedby a single beam splitter, an auxiliary polarization beam splitter maybe additionally provided as shown in FIGS. 35A and 35B. That is, in theabove image display apparatus, the reflector 33 is located following twopolarization beam splitters 35 and 32 laid downstream of the field lens21, and the modulator 31 is located at the lateral side of the secondpolarization beam splitter 32. Also, an optical path length adjustingblock 36 is provided at the lateral side of the first polarization beamsplitter 35 and a reflector 37 is provided at the lateral side of theoptical path length adjusting block 35. These reflector 33, modulator 31and reflector 37 are located to have an equal optical path length fromthe field lens 21, namely, from the inner reflecting planes of thepolarization beam splitters 32 and 35, respectively. The twopolarization beam splitters 35 and 32 are in such a geometric relationthat the light beams are reflected by the planes of reflection inorthogonal directions.

[0210] In this image display apparatus, the recycled light can bereturned to the modulator 31 as in the image display apparatus havingbeen illustrated and described with reference to FIG. 34A, and the twotandem polarization beam splitters can attain a larger opticalextinction ratio.

[0211] Further, in case three modulators for three primary colors: red(R), green (G) and blue (B), respectively, the reflector 33 is locatedfollowing the polarization beam splitter 32 and optical path lengthadjusting block 36 laid downstream of the field lens 21, and modulators31 a, 31 b and 31 c are provided at the lateral side of the polarizationbeam splitter 32 as well as in pair with color separation prisms 37, 38and 39, respectively, as shown in FIG. 36. The reflector 33 andmodulators 31 a, 31 b and 31 c are located to have an equal optical pathlength from the field lens 21, namely, from the inner reflecting planeof the polarization beam splitter 32, through the color separationprisms 37, 38 and 39.

[0212] In the above image display apparatus, the illumination light isseparated by the color separation prims 37, 38 and 39 into the threeprimary colors (R, G and B), the modulators 31 a, 31 b and 31 c modulatethe separated colors according to R (red), G (green) and B (blue),respectively, of an image to be displayed, and the light beams passedthrough these modulators 31 a, 31 b and 31 c are recombined to displaythe image.

[0213] Note that since the optic axis of the optical system laiddownstream of the condenser lens 10 is shifted in a directionperpendicular to the plane of the drawing (FIG. 36), so the optic-axisshifting is not shown in FIG. 36 but the optical system ranging from thelight source 27 to the field lens 21 is similar in construction to thosein FIGS. 34A and 35A.

[0214] [Construction of the image display apparatus with the reflectivecolor filter]

[0215] Referring now to FIGS. 37A and 38, there are schematicallyillustrated in the form of an axial-sectional view the seventh andeighth embodiments of the image display apparatus according to thepresent invention. Each image display apparatus may additionally includea P-S converter 40 and have the modulator 31 formed from color filterlayers each made of an interference filter and located corresponding toeach pixel, as shown in FIGS. 37A and 38. The image display apparatusincludes the light source 24 with the parabolic mirror 7, fly-eyeintegrator 2, reflector 14 having an aperture pattern, P-S converter 40,condenser lens 10, field lens 11 and modulator 31 located in this order.It should be noted that FIG. 37A shows an axial-section of theilluminator horizontally viewed and FIG. 37B shows an axial-sectionvertically viewed. As shown in FIG. 37B, the modulator 31 is laidobliquely in relation to the optic axis.

[0216] As having previously been described with reference to FIG. 2, theP-S converter 40 is formed as follows. Namely, a glass block is preparedby attaching glass plates each having formed thereon a polarizedcomponent separating layer formed from a multilayer film of an inorganicsubstance and glass plates each having a reflecting surface formedthereon alternately to each other, and the thus formed glass block issliced along cutting planes being at an angle to the joined surfaces ofthe glass plates. The slice is used as the P-S converter 40. When alight beam of a mixture of P- and S-polarized components is incidentupon the P-S converter 40, the P- and S-polarized components areseparated at the polarized component separating layer. Namely, the P-and S-polarized components are separated at each layer of the P-Sconverter 40 and go out of the latter. By placing a half-wave (λ/2)plate at the side of the P-S converter 40, corresponding to the P- orS-polarized component and from which the light goes out, a light beamincluding solely either the P- or S-polarized component can be provided.

[0217] As shown in FIG. 39, the modulator 31 includes a transparentsubstrate 41, a layer in which reflecting shading layers 42 andreflective color filters 43 are alternately arranged, a transparentelectrode 44, an oriented layer 45, a liquid crystal layer 46, anoriented layer 47 and an oriented TFT substrate 48 located in thisorder. The reflective color filter 43 is an interference filter or thelike to allow predetermined color light to pass through and reflectunwanted color light other than the predetermined color light withoutabsorbing them.

[0218] In the image display apparatus, the reflective color filter 43and reflective shading layer 42 work as the first reflecting element.These reflective color filter 43 and reflective shading layer 42, andalso the modulator 31, are laid obliquely in relation to the optic axis.The reflective color filter 43 and reflective shading layer 42 areoblique in a direction rotated about a direction perpendicular to thelength of the attachment surface of the P-S converter 40.

[0219] In this image display apparatus, unwanted component of theprimary light emitted from the light source 24 and not passed througheach reflective color filter 43 is reflected by the reflective colorfilter 43 and reflective shading layer 42. For example, the color filterfor R (red) reflects B (blue) and G (green) color light which willreturn as recycled light to the reflector 14. This is also true for thecolor filters for the other colors. The light beam having thus returnedto the reflector 14 and reflected by the latter is incident again upon aposition symmetric with respect to the optic axis of the modulator 31.At this time, the recycled light will not always return to the filterfor the same color as that when the light has been reflected as theunwanted light. So, the illumination light is recycled.

[0220] Note that in the illuminators shown in FIGS. 37A and 38, the P-Sconverter 41 is of a conventional construction but it may be areflecting polarizer. In this case, the reflecting polarizer should belaid with the oblique direction thereof being perpendicular to that ofthe layer including the reflective color filter and reflective shadinglayer (namely, the oblique direction of the modulator 31). Also, use ofa light source with a quarter-wave plate divided into plural radialzones (even number of radial zones) symmetric with respect to the opticaxis makes it unnecessary to use any P-S converter. Since use of a P-Sconverter will not increase the Etendue of the modulator in this case,the reflection by the reflective color filter improves the efficiency oflight recycling. That is, the above illuminator will be effective whenthe modulator has no sufficient Etendue.

[0221] Also, the oblique setting of the modulator will result in thatthe modulator is set obliquely in relation to the optic axis of aprojection lens (not shown) which forms the image of the modulator onthe screen. If the oblique setting of the modulator in relation to theoptic axis of the projection lens degrades the imaging characteristic onthe screen, the optic axis of the projection lens may be set obliquecorrespondingly to the oblique angle of the modulator.

[0222] Further, the reflective color filter may be made of a cholestericliquid crystal polymer layer of which the helical pitch is adjustedcorrespondingly to each pixel.

[0223] [Construction of the illuminator for the reflecting modulatorwith the reflective color filter]

[0224] Referring now to FIG. 40, there is schematically illustrated inthe form of an axial-sectional view the eighth embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus includes the illuminator 27 with the spheroidalmirror 16 and quarter-wave plate 18 divided into plural (an even numberof) radial zones symmetric with respect to the optic axis, relay lensblock 49 consisting of two pieces between them a toroidal reflector 14having a central opening and a quarter-wave plate 50, field lens 21,reflecting circular polarizer 19, quarter-wave reflector 51, fly-eyeintegrator 2, condenser lens 10, field lens 11 and polarization beamsplitter 32 laid in this order.

[0225] In this image display apparatus, the optic axis of the opticalsystem laid downstream of the field lens 11 is laid obliquely inrelation to that of the optical system laid down to the condenser lens10. In addition, there is provided at the lateral side of the polarizedbam splitter 32 the reflecting modulator 31 formed from an interferencefilter whose color filter layers are laid correspondingly to pixels.

[0226] In the above image display apparatus, S-polarized light from thereflecting plane of the polarization beam splitter 32 illuminates themodulator 31 which will provide a modulated P-polarized light. TheP-polarized light is passed through the polarization beam splitter 32and projected onto a projection lens (not shown).

[0227] As shown in FIG. 41, the modulator 31 in this image displayapparatus is constructed out of a substrate 41, reflective color filter43, transparent electrode 5244, oriented layer 45, liquid crystal layer46, oriented layer 47, reflective electrode and an active matrixsubstrate 53 provided in this order.

[0228] Also, in the modulator 31, the reflective electrode 52 shoulddesirably formed correspondingly to the effective pixel range and areflector 54 desirably be formed in the ineffective range along theeffective pixel range, as shown in FIG. 42. The range in which themodulator 31 is to be illuminated is generally defined large than theeffective matrix range for the tolerance of assembling precision. Also,by forming the reflector 54 to be larger than the range of illumination,it is also possible to recycle the illumination light projected upon theineffective range other than the display range.

[0229] In the image display apparatus, the reflective color filter 43,reflective electrode 52 and reflector 54 work together as the firstreflecting element. This embodiment is intended for an improvedefficiency of color utilization as well as for an improved peakbrightness.

[0230] In the image display apparatus, the light beam emitted from thelamp bulb 12 in the light source 27 is polarized in a constant directionby the polarized-state converting function of the light source 27,namely, S-polarized in relation to the reflecting plane of thepolarization beam splitter 32 to illuminate the modulator 31.

[0231] The primary light emitted from the light source 27 has theunwanted light, included therein and not passing through the reflectivecolor filter 43 in the modulator 31, reflected by the color filter 43.For example, the color filter for R (red) reflects B (blue) and G(green) color light. These reflected color light beams return to thereflector 14. The light incident upon the reflector 14 passes throughthe quarter-wave plate 50 on the reflector 14 which will linearlypolarize the light. The recycled light reflected by the reflector 14passes, as a circularly polarized light, through the reflecting circularpolarizer 19. The recycled light is incident again upon the reflectivecolor filter 43. At this time, the recycled light will not always returnto the filter for the same color light as those reflected as theunwanted light. Thus, the light is recycled.

[0232] Similarly, the light not modulated by the modulator 31 isreturned to the reflector 14 where it will be uniformed to illuminatethe entire modulator 31. The light reflected again by the reflectivecolor filter 43 and light not modulated pass through the central openingof the reflector 14 and return to the light-emission point of the lightsource 27.

[0233] Also, of the light emitted from the light source 27 and incidentupon the reflecting circular polarizer 19, a circularly polarized in adirection in which it is reflected by the reflecting circular polarizer19 is reflected by the reflecting circular polarizer 19 and returnsagain to the light-emission point of the light source 27. When the lightis incident again upon the reflecting circular polarizer 19, it has beencircularly polarized in a direction in which will pass through thereflecting circular polarizer 19. When it passes trough the reflectingcircular polarizer 19 and also through the quarter-wave plate 51, it isS-polarized in relation to the reflecting plane of the polarization beamsplitter 32 to illuminate the modulator 31. With the above processrepeatedly done, the light is recycled with an improved efficiency.

[0234] [Construction of the recycle-type sequential color image displayapparatus]

[0235] Referring now to FIG. 43, there is schematically illustrated inthe form of an axial-sectional view, the ninth embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus may be constructed out of the light source 24with the parabolic mirror 7, fly-eye integrator 2, reflector 14 havingan opening formed therein, P-S converter 40, condenser lens 10, fieldlens 11, sequential color shutter 55, reflecting polarizer 6 andmodulator 31 located in this order as shown in FIG. 43. In this imagedisplay apparatus, the optic axis of the optical system laid downstreamof the condenser lens 10 is laid shifted in parallel to that of theoptic axis of the optical system ranging from the light source 24 to thereflector 14.

[0236] In this image display apparatus, a single-plate color display isimplemented as in the aforementioned embodiment and the color display ismade by the use of a sequential color display. That is, the sequentialcolor shutter 55 uses th reflecting polarizer 6 as an analyzer therefor.In this illumination optical system, unwanted light not related with theimage display at each time point is reflected by the reflectingpolarizer 6 to return the light to the reflector 14, whereby it is madepossible to recycle the illumination light.

[0237] [Construction of the illuminator for an improved peak brightness(1)]

[0238] Referring now to FIG. 44A, there is schematically illustrated inthe form of an axial-sectional view the tenth embodiment of the imagedisplay apparatus according to the present invention. As shown, thisimage display apparatus may include two fly-eye integrator groups 2 and25. In this case, the uniformity of the recycled light can be improved.

[0239] More specifically, the image display apparatus includes, as shownin FIG. 44A, the light source 24 with the parabolic mirror 7, fly-eyeintegrator 25, reflector 14, fly-eye integrator 2, P-S converter 40,condenser lens 10, field lens 11 and polarization beam splitter 32located in this order, and also the modulator (reflective liquid crystalpolymer-made modulator) 31 provided at the lateral side of thepolarization beam splitter 32. The light passed through the polarizationbeam splitter 32 via the modulator 31 is projected by a projection lens67 onto a screen 68 as shown in FIG. 44B.

[0240] The first fly-eye integrator 2 is formed from an element having asimilar shape to that of the to-be-illuminated object. The secondfly-eye integrator 25 disposed between the first fly-eye integrator 2and light source 24 may be different in shape from the first fly-eyeintegrator 2.

[0241] The second fly-eye integrator 25 forms the relay-condenserillumination system, and the reflector 14 as the second reflectingelement is laid in a zone near the aperture and where it will not shadethe primary light.

[0242] Also, the optic axis of the optical system laid downstream of thecondenser lens 10 is shifted by about a quarter of the element pitch ofthe first fly-eye integrator 2 in parallel to that of the rest of theoptical system. Further, the element pitch of the first fly-eyeintegrator 2 is set different from that of the second fly-eye integrator25.

[0243] In the image display apparatus, the recycled light returning tothe light source 24 after passing through the modulator 31 forms apattern of reflected light on each element of the first fly-eye lens 8of the first fly-eye integrator 2. Since the element pitch of the secondfly-eye integrator 25 is different from that of the first fly-eyeintegrator 2, the recycled light is incident upon the reflector 14,reflected by the latter, and incident again upon the first fly-eye lens8 of the first fly-eye integrator 2. At this time, the recycled lightwill form a pattern different from that formed when it has initiallyreturned to the first fly-eye lens 8. Therefore, the recycled lightpasses through the first fly-eye integrator 2, and is incident upon thefirst reflecting element 6. At this time, the light has an uniformedintensity.

[0244] In this image display apparatus, there may be provided a colorseparation/recombination prism to display an image in colors, or a colorfilter as in the aforementioned embodiment. The optic axis of theoptical system laid downstream of the condenser lens 10 should desirablybe disclosed in a direction in which the distance between the field lens21 and the reflecting plane of the polarization beam splitter 32 willnot be changed by shifting the optic axis. This is intended to allow anincrease of the angle of light beam incidence, corresponding to theshift of the optic axis.

[0245] Also, the P-S converter 40 may be replaced with anotherpolarized-state converter. For example, there may be provided thereflector 33 to reflect the light coming from the field lens 11 andpassed through the polarization beam splitter 32 and there may also beprovided the reflector 14 between the fly-eye integrator 2 and condenserlens 10, as shown in FIGS. 45A and 45B. The reflector 33 is laidobliquely in relation to the optic axis. The reflector 33 is setobliquely in a direction perpendicular to the direction of shifting theoptic axis of the optical system laid downstream of the condenser lens10.

[0246] Further, by using a light source with a quarter-wave platedivided into plural (an even number of) radial zones symmetric withrespect the optic axis, it is made unnecessary to use any P-S converter.In this case, since the Etendue will not be increased by the use of aP-S converter, the reflection of the illumination light by thereflective color filter will improve the efficiency of light recycling.That is, this measure is effective when the modulator has no sufficientEtendue.

[0247] In the image display apparatus, the illumination not modulated bythe modulator 31 returns as recycled light to the light source 24through the polarization beam splitter 32. The recycled light reflectedat the reflector 14 is uniformed by the fly-eye integrator 2 touniformly illuminate the modulator 31.

[0248] Also in the above case, a bright zone within a dark displayedimage can be displayed brighter. FIG. 46 graphically shows the variationin peak intensity of a displayed image in the eleventh embodiment of theimage display apparatus according to the present invention. As shown,the relation between the mean brightness and peak brightness is suchthat the larger the Etendue of the modulator, the larger number of timesthe light can be recycled and the lower the mean brightness of thedisplay screen, the brighter the bright zone depicting an exponentialascending curve. Since the black level increases at the same rate, thecontrast of the image display apparatus itself will not change. However,in case the contrast of the apparatus as a projector depends upon theincrease of the black level due to the reflection of external light, itis improved.

[0249] Note that generally, also in an illuminator including thereflecting modulator and polarization beam splitter, the unwanted lightwill return to the light source but if there is not any means forrecycling the unwanted light by returning the light to the modulatorpositively and efficiently, the light cannot be recycled effectively.

[0250] [Construction of the illuminator for improved peak brightness(2)]

[0251] Referring now to FIG. 47, there is schematically illustrated inthe form of an axial-sectional view the twelfth embodiment of the imagedisplay apparatus according to the present invention. As shown, theimage display apparatus includes the light source 27 with the spheroidalmirror 16, relay lens 28, field lens 29, reflector 14 having an openingformed therein, rod integrator 26, condenser lens 30, relay lens 20,reflector 14 c, condenser lens 10, field lens 21, reflecting polarizer6, transmissive modulator 31, and another reflecting polarizer 6 as ananalyzer, located in this order. The optic axis of the optical systemlaid downstream of the condenser lens 10 is shifted in parallel to thatof the optical system ranging from the light source 27 to the relay lens20.

[0252] In this image display apparatus, the light source 27 andreflecting polarizer 6 provide the function to convert the polarizedstate of light. As in the aforementioned embodiment, the reflectingpolarizer 6 is formed from a cholesteric liquid crystal polymer-madecircular polarizer.

[0253] The illumination light emitted from the light source 27 passesthrough the relay lens 28, field lens 29, rod integrator 26, condenserlens 30, relay lens 20, condenser lens 10 and field lens 21 and incidentupon the reflecting polarizers 6. One circularly polarized light passesthrough these reflecting polarizers 6 while the other circularlypolarized light is reflected by the reflecting polarizers 6. Thereflected light is incident upon the reflector 14 c, and reflected bythe latter to be an opposite-directional circularly polarized light.This light is incident again upon the reflecting polarizer 6 and passesthrough the latter. The light thus passed through the reflectingpolarizer 6 is incident upon the modulator 31 in which it will undergospatial modulation according to an image to be displayed.

[0254] The reflecting polarizer 6 as the analyzer in the image displayapparatus is a cholesteric liquid crystal polymer-made circularpolarizer formed within the modulator as shown in FIG. 49. As shown, themodulator 31 includes a TFT substrate 48, oriented layer 45, liquidcrystal layer 46, oriented layer 47, transparent electrode 44,reflecting polarizer 6 and substrate 41 laid in this order. In addition,the modulator 31 has an anti-reflection coating 15 formed on either sidethereof. The reflecting polarizers 6 laid before and after the modulator31 are opposite in direction of helicity to each other.

[0255] In the image display apparatus, the light beam not modulated bythe modulator 31 passes the latter, is reflected by the reflectingpolarizer 6 and incident upon the rod integrator 26 or reflector 14 c.The light beam reflected by the reflector 14 c becomes acounter-torsional circularly polarized light, is reflected by thereflecting polarizer 6, and then incident upon the rod integrator 26.The light is uniformed by the rod integrated 26, and is partiallyreflected by the reflector 14 provided along the opening at the end ofthe light source 27 while the rest of the light is returned to the lightsource 27. The recycled light is uniformed by the rod integrator 26, andchanged in polarized state to uniformly illuminate the modulator 31.

[0256] In this image display apparatus, the liquid crystal polymerforming the modulator works in the VA mode. However, by providing aquarter-wave plate between the cholesteric liquid crystal polymer-madecircular polarizer and liquid crystal layer to linearly polarize thelight, the modulator may be caused to work in the TN mode or the likefor the linearly polarized light.

[0257] Referring now to FIG. 48, there is schematically illustrated inthe form of an axial-sectional view the thirteenth embodiment of theimage display apparatus according to the present invention. As shown,the image display apparatus may include three modulators 31 a, 31 b and31 c. That is, the image display apparatus includes the light source 27with the spheroidal mirror 16, relay lens 28, field lens 29, reflector14 having an opening formed therein, rod integrator 26, condenser lens30, relay lens 20, reflector 14 c and condenser lens 10 provided in thisorder. In this image display apparatus, an illumination optical systemis formed from the above components with the optic axis of the condenserlens 10 being shifted in parallel to that of the optical system rangingfrom the light source 27 to the relay lens 20, to guide the outgoinglight from the optical system to a first spectral reflecting mirror 57via a mirror 56.

[0258] The first spectral reflecting mirror 57 allows the R (red) lightto pass through while reflecting the G (green) and B (blue) light, forexample. The R (red) light is reflected by a mirror 62, passes through arelay lens 64, reflecting polarizer 6, transmissive modulator 31 b andreflecting polarizer 6 as an analyzer, and is incident upon arecombining prism 66. The G (green) and B (blue) light rays are incidentupon a second spectral reflecting mirror 58 where the G (green) light isallowed to pass through while the B (blue) light is reflected. The G(green) light passes through a relay lens 60, reflecting polarizer 6,transmissive modulator 31 a and reflecting polarizer 6 as the analyzer,and is incident upon the recombining prism 66. The B (blue) light passesthrough a relay lens 61 and is reflected bu a mirror 63, passes througha relay lens 65, reflecting polarizer 6, transmissive modulator 31 c andthe reflecting modulator 6 as an analyzer, and is incident upon therecombination prism 66.

[0259] At the recombination prism 66, the R (red), G (green) and B(blue) light rays are recombined and projected towards a projection lens(not shown). The light is projected through the projection lens onto thescreen.

[0260] In the aforementioned embodiments of the present invention, themodulator is formed from a liquid crystal. The light modulated by themodulator is projected onto the screen through the projection lens (notshown). The material of the modulator is not limited to the liquidcrystal but may be formed from any other suitable material. Forimprovement of the efficiency of light recycling, the construction ofthe illumination optical system is not limited to the aforementionedones but it may be a one including a reflecting means provided in anoptimum position of the light source and which would be able to improvethe efficiency of light recycling.

[0261] As having been described in the foregoing, the present inventionprovides inexpensive separation and recombination of polarizedcomponents of a light beam by means of a light source and illuminator,which work together to efficiently recycle unwanted light in theprojector. Also, in case the single-plate modulator using a color filteris used, the light can be utilized with an improved efficiency. Also,use of the sequential color-type single-plate modulator permits toimprove the efficiency of light utilization. Further, the efficiency oflight utilization of an modulator having a low numerical aperture can beimproved, so that the peak brightness on a dark screen can be elevated.

[0262] That is, the present invention provides an image displayapparatus including including a non-luminous modulator, illuminator toilluminate the modulator and a projection lens, and which is simplyconstructed and thus easy to produce and can utilize light with animproved efficiency.

What is claimed is:
 1. A projection-type image display apparatusincluding an illuminator with a light source, optical modulatorilluminated by light from the illuminator and which makes spatialmodulation of the illumination light according to a to-be-displayedimage for either transmission or reflection, and a projection lens toform an image of the optical modulator, the apparatus comprising: afirst reflecting element to reflect, towards the light source, unwantedone of a light beam emitted from the illuminator and that will notilluminate the optical modulator; and a second reflecting element toguide, by reflecting, the unwanted light once reflected by the firstreflecting element to the optical modulator.
 2. The apparatus as setforth in claim 1, wherein the light source is a discharge lamp formedfrom a glass tube having an anti-reflection coating formed on at least apart of the surface thereof.
 3. The apparatus as set forth in claim 1,wherein the first reflecting element is positioned not to shade theillumination light emitted from the illuminator towards the opticalmodulator.
 4. The apparatus as set forth in claim 1, wherein theilluminator includes a light source, reflector whose section isspheroidal, and a condenser lens whose diameter is generally the same asan end of the reflector at which the light will go out.
 5. The apparatusas set forth in claim 4, wherein the light source is positionedgenerally coincident with a first focal point of the reflector; and thecondenser lens is positioned to have the light source-side focal pointthereof generally at a second focal point of the reflector.
 6. Theapparatus as set forth in claim 1, wherein the illuminator includes anillumination optical system to guide the light beam emitted from thelight source to the optical modulator; the illumination optical systemincludes an integrator to uniform the light intensity distributionwithin the light beam; and the first reflecting element is positioned tobe generally conjugate with the integrator with the illumination opticalsystem being laid between them.
 7. The apparatus as set forth in claim6, wherein the illumination optical system forms a telecentric opticalsystem in the first reflecting element.
 8. The apparatus as set forth inclaim 1, wherein the illuminator includes an illumination optical systemto guide the light beams emitted from the light source to the opticalmodulator; and the first reflecting element is positioned in a planeincluding a point generally conjugate with a point of light emission ofthe light source with the illumination optical system being laid betweenthem not to shade the illumination light traveling from thelight-emission point to the optical modulator.
 9. The apparatus as setforth in claim 8, wherein the illumination optical system forms atelecentric optical system in the first reflecting element
 10. Theapparatus as set forth in claim 8, wherein the illumination opticalsystem includes an integrator to uniform the light intensitydistribution within the light beam and a relay-condenser optical systemlaid between the integrator and light source; and the first reflectingelement is positioned near the relay-condenser optical system not toshade the illumination light traveling from the light source to theoptical modulator.
 11. The apparatus as set forth in claim 8, whereinthe first reflecting element is positioned obliquely in relation to theoptic axis of the illumination optical system.
 12. The apparatus as setforth in claim 8, wherein the illumination optical system includes afly-eye integrator to uniform the light intensity distribution withinthe light beam and a condenser lens upon which the light beam passedthrough the fly-eye integrator is incident; and the first reflectingelement is provided between the fly-eye integrator and condenser lens.13. The apparatus as set forth in claim 12, wherein the optic axis ofthe optical system laid downstream of the condenser lens is shifted inparallel to that of the optical system ranging from the light source tothe fly-eye integrator.
 14. The apparatus as set forth in claim 1,wherein the illuminator includes an illumination optical system to guidethe light beam emitted from the light source to the optical modulator;the illumination optical system includes an integrator to uniform thelight intensity distribution within the light beam; and the optic axisof the optical system laid downstream of the integrator is shifted inparallel to that of the optical system ranging from the light source tothe integrator.
 15. The apparatus as set forth in claim 14, wherein thefirst reflecting element is positioned between the light source andintegrator not to shade the illumination light traveling from the lightsource to the optical modulator.
 16. The apparatus as set forth in claim1, wherein the illuminator includes an illumination optical system toguide the light beam emitted from the light source to the opticalmodulator; the illumination optical system includes a rod integrator asthe integrator to uniform the light intensity distribution within thelight beam; and the first reflecting element is positioned near thelight-incident end face of the rod integrator not to shade theillumination light traveling from the light source to the opticalmodulator.
 17. The apparatus as set forth in claim 1, wherein theilluminator includes an illumination optical system to guide the lightbeam emitted from the light source to the optical modulator; theillumination optical system includes a rod integrator as the integratorto uniform the light intensity distribution within the light beam, and acondenser lens to form an image of the rod integrator; and the opticaxis of the optical system ranging from the light source to the rodintegrator is shifted in parallel to that of the optical system laiddownstream of the condenser lens.
 18. The apparatus as set forth inclaim 17, wherein the first reflecting element is positioned between therod integrator and condenser lens not to shade the illumination lighttraveling from the light source to the optical modulator.
 19. Theapparatus as set forth in claim 1, wherein the first reflecting elementis a reflecting polarizer.
 20. The apparatus as set forth in claim 19,wherein the reflecting polarizer is a reflecting circular polarizer. 21.The apparatus as set forth in claim 20, where the reflecting polarizeris formed from a cholesteric liquid crystal polymer layer.
 22. Theapparatus as set forth in claim 21, wherein the cholesteric liquidcrystal polymer layer has an anti-reflection coating formed on theair-contact surface thereof.
 23. The apparatus as set forth in claim 19,wherein the reflecting polarizer is a reflecting linear polarizer. 24.The apparatus as set forth in claim 23, wherein a quarter-wave (λ/4)plate is laid between the reflecting linear polarizer and a secondreflecting element.
 25. The apparatus as set forth in claim 1, whereinthe first reflecting element is a combination of a polarization beamsplitter and a reflector.
 26. The apparatus as set forth in claim 25,wherein a quarter-wave plate is provided between the polarization beamsplitter of the first reflecting element and a second reflectingelement.
 27. The apparatus as set forth in claim 1, wherein the firstreflecting element is a shading layer formed inside the opticalmodulator.
 28. The apparatus as set forth in claim 1, wherein the firstreflecting element is a reflective color filter formed inside theoptical modulator.
 29. The apparatus as set forth in claim 1, furthercomprising a sequential color shutter; the first reflecting elementserving also as an analyzer of the sequential color shutter.
 30. Theapparatus as set forth in claim 1, wherein the first reflecting elementis an analyzer of the optical modulator.
 31. The apparatus as set forthin claim 30, wherein the analyzer is formed inside the opticalmodulator.
 32. The apparatus as set forth in claim 31, wherein theanalyzer is formed from a cholesteric liquid crystal polymer layer. 33.The apparatus as set forth in claim 32, wherein the cholesteric liquidcrystal polymer layer has an anti-reflection coating formed on theair-contact surface thereof.
 34. The apparatus as set forth in claim 1,wherein the first reflecting element is a reflecting optical modulator.35. The apparatus as set forth in claim 1, wherein the illuminatorincludes a discharge lamp as a light source and a reflector having thesectional form of a paraboloid of revolution; and a phase-differenceplate and a reflecting polarizer are provided in the optical pathbetween the discharge lamp and optical modulator.
 36. The apparatus asset forth in claim 35, wherein the phase-difference plate is dividedalong radial boundary lines concentric to the center axis of thereflector into plural zones whose retardation axes extend in differentdirections.
 37. The apparatus as set forth in claim 36, whereinretardation axes of those zones of the phase-difference plate which arephase-retardation axis with respect to the center axis of the reflector,extend perpendicular to each other.
 38. The apparatus as set forth inclaim 35, wherein the reflecting polarizer is a circular polarizer; andthe phase-difference plate is a quarter-wave plate.
 39. The apparatus asset forth in claim 35, wherein the reflecting polarizer is a circularpolarizer; and the phase-difference plate is a half-wave (λ/2) plate.